Definition of "shrinkage"

How far progress has been made in liquidating the locomotive stock of the old companies may be judged from the shrinkage in their numbers, by some 50 per cent. at the end of 1931, to about 35 per cent. in 1938.

1939 September, D. S. Barrie, “The Railways of South Wales”, in Railway Magazine, page 161

An emergency South Western Railway (SWR) timetable came into force on September 5, in response to the shrinkage of clay embankments on the nine miles between Gillingham and Tisbury. The shrinkage has been caused by the driest summer since 1936, with a severe 40mph speed restriction having to be imposed.

2022 September 21, “Network News: West of England Line average speeds drop... to just 31mph”, in RAIL, number 966, page 18

Do women know about shrinkage?

1994 Peter Mehlman & Carol Leifer, "The Hamptons," Seinfeld, Season 5, Episode 20 (aired May 12, 1994), Spoken by Jerry Seinfeld (Jerry Seinfeld)

This is why guys experience "shrinkage" after they've been swimming.

2006, Steve Gerali, Teenage Guys: Exploring Issues Adolescent Guys Face and Strategies to Help Them, Zondervan, page 63

That'll get their blood flowing... getting the blood flowing coz just the mere thought of jumping into that icy water was starting to get the shrinkage going.

2008, Anthony William Brownless, Billy's Book for Blokes, Allen & Unwin

And of course, one of the most important questions of all, especially among male plungers, is, "What about shrinkage?!"

2010, Fran Capo, Art Zuckerman, Susan Zuckerman, “Polar Bear Clubs”, in It Happened in New York City: Remarkable Events That Shaped History, Globe Pequot, page 51

Next, on with his favourite budgie smugglers. His sequined posing pouch. No winky shrinkage for him.

2023 April 21, John Crace, “Psycho goes down raging: the liberal wokerati finally get to Raab”, in The Guardian‎